The invention relates to the field of electric analysis of light images using charge transfer in a semiconductor; it has as object a device more particularly adapted to the analysis of color images.
Different solid state devices are known for analysing a light image, which are for use in a television camera for supplying a video electric signal. They are distinguished by the embodiment of the photosensitive zone on the one hand and the system for reading and removing the charges created by the image, on the other hand.
The use of charge transfer devices is already known for providing these different functions, as is described for example in the work by SEQUIN and TOMPSETT, entitled "Charge transfer devices", (pages 152 to 169);
in so-called "frame transfer" or "interline structure" organizations, in which the light radiation is received on charge transfer registers; in these devices, the charge transfer is carried out over large areas, which constitutes a disadvantage because it is at present difficult to obtain high outputs in the manufacture of these large surfaces; PA1 in so-called "CID" devices (for "Charge injection devices") which do not present this drawback but which generally require reinjection of the charges into the semiconductor substrate, which presents a number of disadvantages among which noise and difficulties at the level of the values of the capacities required during or after reading of the charges. PA1 a matrix of N lines.times.M zones, or photosensitive points, on to which matrix an image to be read is projected and converted into electric charges; PA1 an M points memory, so-called line memory, intended to receive successively the signal charges stored by each line; PA1 a shift register of the CCD type (for "charge coupled devices") receiving in parallel the contents of the line memory and delivering in series the electric analysis signal of the image. PA1 a plurality of elementary photosensitive zones, called points, in which electric charges are created depending on the illumination received, formed on the same semiconductor substrate in N lines and M columns, isolated from each other and forming a matrix, each of these elementary zones comprising an MOS capacity, forming a first charge collection zone and comprising a grid which is common to the capacities of the same line, and a second charge collection zone, electrically coupled to the capacity, the whole of the point receiving a colored filter intended to make it sensitive only to a pre-defined color; PA1 connection and control means, providing in parallel, through column connections, electric charges created in the M points of the same line, successively for the N lines, these means comprising a plurality of reading diodes, arranged in columns between the points so as to receive each one, successively, to order, the charges from at least two points belonging to two different lines; PA1 means forming a screen for the charges, placed between each of the points and the connection means, these screen means comprising a plurality of grids, brought to a constant potential, arranged in columns between the reading diodes and the points; PA1 an assembly of two memories of M points each one, called line memories, formed in the same semiconductor substrate, receiving in parallel the electric charges provided by the connection and control means so that each point in the matrix is assigned to one only of the two line memories, one of these memories being connected only to the points of the same color; PA1 an assembly of two analog shift registers, receiving in parallel respectively the charges supplied by the two line memories and each one delivering in series an electric analysis signal of the image.
More generally, in addition to the above-mentioned problems, there arises the question of the compatibility of the times required, on the one hand, for light integration and, on the other hand, for the transfer of the charges in the case where this solution is selected, with times for scanning the television screen which are, in the usual 625 line standard, about 52 .mu.s for the display time of a line and 12 .mu.s for the line return time.
To comply with these different requirements, the Applicant has proposed a so-called "line transfer" structure, described in French patent application No. 80-08112, which principally comprises: